1. Field of the Invention
The present invention relates to a projector, and more particularly to a projector having a plurality of cameras for capturing an image projected onto a screen.
2. Description of the Related Art
In recent years, projectors have been improved to the point where they can be used in a variety of applications. In view of the wide range of applications, it is desirable for the operator to be able to install the projector simply under optimum conditions. To meet such a demand, it is necessary to adjust the focus of projected images to make the projected images sharp and also to correct projected images out of distortion when images are projected from projectors which swings from side to side and tilts or when images are projected onto shaped surfaces of projection objects.
One known rangefinder for use in focus adjustments is an optical shape sensor disclosed in Japanese laid-open patent publication No. 2003-42733. The disclosed optical shape sensor has light-emitting elements for applying a plurality of variable-amount light beams modulated with a certain frequency to a surface to be measured, and detecting elements for detecting reflected light beams only in a certain direction. The optical shape sensor acquires distance information from phase information that is obtained from the detected light beams.
Japanese laid-open patent publication No. H9-281597 discloses a liquid crystal projector which performs a process of correcting a projected image out of distortion. The liquid crystal projector has an angle detecting means for detecting an angle at which the projector is installed, and a distance detecting means for detecting the distance between the projector and an object onto which an image is projected from the projector. The angle of a liquid crystal display unit of the projector is adjusted to an angle which is calculated based on the angled detected by the angle detecting means and the distance detected by the distance detecting means.
Japanese laid-open patent publication No. 2000-122617 reveals a trapezoidal distortion correcting apparatus having a plurality of distance sensors mounted at different positions on the front face of a liquid crystal projector housing. The trapezoidal distortion correcting apparatus also has a control microcomputer which calculates an angle of tilt of the liquid crystal projector housing with respect to the screen based on distances detected by the distance sensors, and decimates pixel data of scanning lines to produce a trapezoidal distortion which is a reversal of the trapezoidal distortion that is actually present in a projected image, based on the calculated angle of tilt.
Conventional processes for adjusting the focus of projected images to make the projected images sharp and also to correct projected images out of distortion when images are projected from projectors which swings from side to side and tilts or when images are projected onto shaped surfaces of projection objects are problematic in that the processes are tedious and time-consuming.
The optical shape sensor disclosed in Japanese laid-open patent publication No. 2003-42733 allows focus adjustments to be made automatically, but needs to be combined with other means for making other adjustments.
Though the processes disclosed in Japanese laid-open patent publication No. H9-281597 and Japanese laid-open patent publication No. 2000-122617 can automatically correct projected images out of distortion, they need to make other adjustments in combination with other means.
When a projector is used to make a presentation, if images projected by the projector are large, then the presenter occasionally needs to stand in front of a projection object, i.e., an object to project images onto, such as a screen, to explain. One problem that occurs when the presenter stands in front of the screen is that the presenter is annoyed by the glare of strong light emitted by the projector which enters the eyes of the presenter.
While making a presentation using a projector, the presenter often needs to change projected images and/or write onto the projected images as the presentation progresses. Heretofore, since the presenter uses a remote controller or a mouse to control the projector, it is not easy to change projected images and/or write onto the projected images while standing in front of the screen.
The conventional practice has been to use a camera in combination with a projector for correcting the projected position of a projected image or for correcting a projected image out of distortion. The conventional correcting process that uses a camera is based on the assumption that the projection object is a flat surface. If the projection object is a screen, then the camera can only detect the outer frame of the screen. Therefore, if the projection object is a curved surface, but not a flat surface, then projected images that are distorted cannot be properly corrected. In this application, “a curved surface” means all kinds of surface that is not flat. Because the camera detects only the outer frame of the screen, but not the distance to the screen, other means need to be employed to adjust the focus of projected images, to detect a person in front of the projection object, and to detect when the surface of the projection object is touched.